Advances in medical technology and transplantation lead to the re-defining of death to include death by virtue of brain death. The determination of whole brain death requires the demonstration of three things: an irreversible comatose state; the loss of brainstem reflexes; and brainstem inactivity leading to apnea. Protocols for the clinical determination of brain death vary among institutions but must generally be made by more than one doctor in one of several relevant specialties. Neurophysiologic determinations of cerebral circulatory arrest include four-vessel cerebral angiography as well as various scintigraphic perfusion studies. In all countries where brain death is recognized legally, the diagnosis rests with physical examination, at times supported by further medical testing. Philosophical arguments for the integrity of brain death as a definition of death rest in historic religious and social concepts of what constitutes life, or with ideas that loss of personhood may be equivalent to death.